s6-portable-utils is a set of tiny general Unix utilities, often performing well-known tasks such as cut and grep, but optimized for simplicity and small size. They were designed for embedded systems and other constrained environments, but work everywhere. Other sets of small utilities are usually system-specific; for instance, the (otherwise excellent) BusyBox project only works on Linux.
encapsulate provides its client process the same environment it's started in, except for some limitations: encapsulate remounts the whole filesystem read-only, except for user-selectable regions which are mounted read-write. It also isolates the process from the system's process table, network interface, IPC, and shared memory tables.
xstatbar is a minimal system stats viewer for X11. It shows stats for CPU usage (with support for multi-core processors), memory usage, the number of processes, battery usage, volume, and time. It displays as a small, horizontal bar that integrates nicely with tiling window managers.
minidb is a Python module that utilizes the SQLite3 database library in order to store and retrieve Python objects. It utilizes Python's __slots__ mechanism to determine the column names, and uses the class name for table names. Data is always stored as text in the database, but will be converted using the type specified in __slots__ (which therefore has to be a dict).